Timing of bonding changes in fundamental reactions in solutions: pyridinolysis of a triazinylpyridinium salt

Abstract

Pyridinolysis of 1-(4,6-diphenoxy-1,3,5-triazin-2-yl)pyridinium chloride with substituted pyridines in aqueous solution exhibits a non-linear Brønsted correlation possessing a break-point at the pK_a of the pyridine nucleophile equal to that of the leaving group: the results are consistent with the intervention of a Meisenheimer-like intermediate and the full effective charge map for solution states along the reaction coordinate indicates substantial bonding change in the formation of the transition states.